1 Technical Field
The present invention relates generally to a semiconductor module which includes a resin molded package equipped with a power semiconductor chip and a heat spreader working to spread heat from the power semiconductor chip and which may be of a 1-in-1 structure into which a single power semiconductor chip(s) such as an IGBT or a power MOSFET for use as either of an upper arm (i.e., a high side device) or a lower arm (i.e., a low side device) of an inverter is resin-molded, or a 2-in-1 structure into which two power semiconductor chips for use as the upper and lower arms, respectively, are resin-molded. The present invention also relates to a production method of such a semiconductor module.
2 Background Art
One of typical semiconductor modules is equipped with a resin molded package in which a semiconductor chip(s) with a semiconductor power device and heat spreaders serving to dissipate heat, as generated by the semiconductor power device, are disposed. Some of such a type of semiconductor modules are also equipped with a fin heat sink formed integrally with each of the heat spreaders in order to enhance dissipation of the heat generated by the semiconductor power device. The heat spreader is so installed as to expose the fin heat sink to a cooling fluid such as water fed from a cooling mechanism installed in the semiconductor module to transfer the heat to the cooling fluid.
Japanese Patent First Publication No. 2006-165534 discloses heat spreaders which are so disposed as to face each other. Coolant flows between the heat spreaders to cool semiconductor power devices. In order to enhance such cooling efficiency, the heat spreaders have irregularities formed facing surfaces thereof which work as fin heat sinks. All the heat spreaders and the cooling fins are made of metal, which may result in electrical leakage between the facing surfaces of the heat spreaders.
In order to achieve a high degree of the cooling efficiency of the heat spreaders and the electrical insulation between the spreaders at the same time, it is effective to form insulating films on the fin heat sinks. A difficulty is, however, encountered in forming the insulating films on the uneven surface of the fin heat sinks. Such formation may be achieved in the vapor phase epitaxial method such as spattering, CVD, or spray coating. It is, however, difficult for such a method to achieve a constant thickness of coating of insulator between fins of the fin heat sink, which may lead to the leakage of electricity from the heat spreader.
To integrate the heat spreader and the fin heat sink, it is usually made by shaving, casting, or extrusion. These methods difficulty in fabricating the pitched fine fins of the fin heat sink and ensuring a desired size of the area of the fin heat sink from which the heat is dissipated.